[A comparison study of anterior chamber depth using A sonography and biomicroscopy in patient with cataract]

To know the difference of measured anterior chamber depth (ACD) in cataract eyes between A-scan and ultrasound biomicroscopy (UBM) measurements.

Case series study, the ACD of 396 patients (480 eyes with cataract) came from the Department of Ophthalmology, Nanjing Drum Tower Hospital between January, 2008 and March, 2010, were measured by A-scan and UBM. Two groups were classified by whether the optical area of anterior cortex was transparent or not: 433 (90.21%) eyes with transparent anterior cortex and 47 (9.79%) eyes with pacific anterior cortex. The former are classified into 3 groups: < 3.0 mm, 3.0 - 3.5 mm, > 3.5 mm, according to the ACD value of UBM. The differences of ACD between A-scan and USB readings was analyzed.

The average ACD value of cataract eyes with transparent anterior cortex was (3.24 ± 0.56) mm (measured by USB) and (3.14 ± 0.56) mm (measured by A-scan), respectively. There was no significant difference between these two measurements (t = 0.128, P = 0.082). In eyes with ACD < 3.0 mm, the average ACD was (2.61 ± 0.26) mm (by UBM) and (2.50 ± 0.29) mm (by A-scan), respectively, with a difference of (0.11 ± 0.10) mm. There was a statistical significant difference between these two measurements (t = 0.744, P = 0.023). The average ACD value of cataract eyes with pacific anterior cortex opacity was (2.51 ± 0.52) mm (by UBM) and (3.84 ± 0.55) mm (by A-scan), respectively, with a difference of (-1.33 ± 0.41) mm. There was a significant difference between these two values (t = 14.792, P = 0.000).

In cataract eyes with transparent optic area of anterior cortex, there is no significant difference between measured ACD by A-scan and UBM. In eyes with ACD less than 3.0 mm, there is a significant difference between measured value by A-scan and UBM. When the optical area of anterior cortex is pacific, A-scan records are much higher than the ACD value measured by UBM.